A conventionally-known fuel property sensor is equipped in a fueling system, which is for supplying fuel to an internal combustion engine, and configured to detect a fuel property, such as alcohol concentration, fuel pressure, or oxidation state of fuel. The fuel property sensor is mounted to, for example, a flange, which covers an opening of a fuel tank. The flange has a fluid passage to flow fuel discharged from a fuel pump equipped in the fuel tank. The flange has an insertion hole, which communicates the fluid passage with an external-air side of the flange. The fuel property sensor has a tubular sensor portion mounted to the fluid passage through the insertion hole.
For example, a Patent document 1 (Publication of Japanese Patent 2943722) discloses a configuration in which the tubular fuel pipe (joint 12 in the Patent document 1) is mounted to the insertion hole (opening 14 in the Patent document 1) of the flange (cap 10 in the Patent document 1). In the Patent document 1, the fuel pipe has a stopper portion 38 being in an annular shape and projected radially outward from the outer wall of the fuel pipe. In the Patent document 1, the stopper portion 38 is mounted on the surface of the flange defining the end of the insertion hole on the external-air side. Thereafter, a U-shaped clip 44 is mounted to the fuel pipe on the opposite side of the fluid passage through the stopper portion 38. The clip 44 is held by a clip holding portion 16 formed on the flange and located on the radially outside of the insertion hole. In this way, the stopper portion 38 is sandwiched between the end surface of the flange and the clip 44 thereby to affix the fuel pipe to the insertion hole of the flange.
It is noted that, in the configuration of the Patent document 1, slight gaps are formed respectively between the stopper portion 38 and the clip 44, and between the clip 44 and the clip holding portion 16, due to manufacturing tolerance. Accordingly, the fuel pipe may repeat minute vibration in the axial direction due to vibration of the vehicle. In general, the wall surface of the flange defining the insertion hole and the fuel pipe are sealed with an O-ring therebetween. Due to the above-described vibration of the fuel pipe, the O-ring and other components may cause ablation or deformation.